weak point
A piece of steel cable placed inside a logginghead that is designed to break at a predetermined tension. If the logging tool becomes stuck in the borehole, there is a danger that the logging cable will break at surface, since this is the place of maximum tension. It is difficult to fish a long length of tangled cable in the
Detailed Explanation
borehole. The weak point is designed to break before the cable, so that the latter can be retrieved, leaving only the logging tool and head in the borehole.